Circular annealing inner cover



Nov. 14, 1950 M. JACOB 2,529,609

CIRCULAR ANNEALING INNER COVER Filed Dec. 22, 1949 14 I" 8 23 lg 33 mmvron. Mame/s A. JACOB Patented Nov. 14, 1950 OFFICE CIRCULAR ANNEALING INNER COVER Morris LQJacob, Pittsburgh, Pa., assignor to Pittsburgh Annealing Box Company, Pittsburgh, Pa., a corporation of Pennsylvania Application December 22, 1949, Serial No. 134,447

5 Claims. 1

This invention relates generally to annealing inner covers and more particularly to circular annealing inner covers arranged to be lowered over a. batch of steel to enclose and protect it while the batch is being heat-treated.

This application is a continuation in part of my application, Serial No. 666,218, filed May 1, 1946, for Circular Annealing Cover, now abandoned.

Annealing inner covers of this character have their open bottom edge embedded in a sand or an oil seal that encircles and is below the hearth on which the steel to'be treated is stacked. The furnace, which is frequently referred to as an outer cover, is lowered over the annealing inner cover and heat is applied to the inner cover for the purpose of heat-treating the steel to the proper annealing temperature and under a regulated atmosphere. Many problems arise in this character of heat-treating furnace. The heat must be conveyed to the annealing inner cover,

then through its walls after which it is conveyed by circulatory gases to the steel therein to normalize the same.

The principal object of this invention is the provision of an annealing inner cover that provides a faster annealing cycle of the batch of steel being treated.

Another object is the provision of an annealing inner cover that requires a lower heat input for annealing a batch of steel therein.

' Another object is the provision of a more efficient inner cover constructed to have a materially longer life than covers of similar character.

Another object is the provision of an annealing inner cover that accelerates the heating and cooling period.

Another object is the provision of a circular annealing inner cover that has substantially twice the surface as that of a cover of similar size.

Another object is the provision of an annealing inner cover capable of expanding and retracting at difierent rates at different locations on the cover, thereby holding distortion to a minimum.

Another object is the provision of a symmetrically constructed annealing cover that is inherently structurally strong and the interior of which is devoid of space occupying projections.

Other objects and advantages occur in the following description and claims.

The accompanying drawings show, for the purpose of exemplification without limiting the inventlon or claims thereto, certain practical embodiments of the invention wherein:

Fig. 1 is a view partly in elevation and partly in section of the annealing inner cover comprising this invention;

Fig. 2 is a top plan view of the structure shown in Fig. 1 with part thereof broken away to show the wall in section;

Fig. 3 is an enlarged end view of one of the seven corrugated plates arcuately curved transversely of the corrugations to a uniform radius of curvature to complete inner cover of Fig. 1;

Fig. 4 is an enlarged detailed view in section showing the foot of the inner cover having only the circular reinforcing bar secured to the bottom of the corrugations;

Fig. 5 is a view similar to Fig. 4 showing a conical band at the foot of the inner cover;

Fig. 6 is a view similar to Fig. 4 showing a circular reinforcing bar and a conical band attached thereto; I

Fig. 7 is a viewsimilar to Fig. 4 showing an annular reinforcing bar at the foot of the corrugated cylinder with a frusto conical band depending from an intermediate portion thereof; and

Fig. 8 is an enlarged view of an annular reinforcing bar cut to fit the corrugations and welded thereto.

Referring to Figs. 1 to 3 of the drawings, the circular annealing inner cover I is fabricated from a plurality of corrugated steel plates 2 each of which is arcuately curved transversely of the corrugations to a uniform radius of curvature that forms a complete corrugated cylinder of predetermined diameter when their adjacent edges are integrally connected together as by welding. The corrugations are formed so that their circular crests and troughs merge tangentially into one another providing considerable depth in the corrugations.

The annealing inner cover is made up of seven of the plates 2 each having nine corrugation crests as illustrated in Fig. 3. As each corrugation is formed in' the plate, the selected arcuate curvature of the plate is set therein and when the plate is completely corrugated it is also arcuately formed to the proper radius of curvature.

The plate edges indicated at 3 and 4 are preferably terminated at complementary positions such as indicated. However, the starting position may be selected any place along the tangential merge between the circular crests and troughs or in the trough itself. The adjacent plate edges are welded together providing the longitudinal joints as indicated at 5 to I l, inclusive, in Fig. 2. When the corrugated plates are completely welded to- 3 gather to form a cylinder, the corrugations are uniform for the complete circumference of the cylinder. In fact, sometimes it is diflicult to find the welded seam; It is important to provide a uniform corrugation in order to have a completely symmetrical inner cover.

The depth of th corrugations is selected to provide a surface area twice that of a smooth cylinder having a diameter substantially equal to the smaller inside diameter of the corrugated cylinder. This depth is obtained by lengthening the tangential merge between the circular crests and troughs. The ordinary rectangular corrugated or channel cover provides relatively small increase in surface area. A standard rectangular corrugated inner annealing cover has a corrugation pitch of six inches; 1. e. six inches between corrugation centers. The depth of these standard corrugations is approximately one and one-half to twoinches. The pitch of the corrugations of the annealing inner cover of Figs. 1 to 3 is three to three and one-half inches and the depth of the corrugations are from two and one-fourth to three and one-half inches. Thus, the selection of over twice the corrugation pitch and a material increase in depth over that previously employed in rectangular corrugated inner covers provides in proportion as much as 60% increase in surface area in the corrugated circular inner cover. This selection of a relatively close pitch and increased depth to increase the area to twice that of a smooth cylindrical inner cover enables one to materially accelerate the heating period of the annealing cycle together with the cooling period. Thus, the time of the whole of the annealing cycle is materially reduced as much as 50% by the use of the corrugated circular annealing inner cover over that of the corrugated rectangular annealing inner cover.

'irmer covers as they would collapse when subjected to such violent temperature differential. Thus, the structural features of the corrugated circular inner annealing cover provides material advancement by increasing production through shortening the annealing cycle by providing a materially faster heat transfer.

The upper end of the circular annealing inner cover is closed by a roof or head cap l2 usually constructed from a heavier gauge than the side plates and shaped to have a fiat annular brim or flange i3 that extends radially and is slightly greater in .diameter than the corrugated cylinder to permit this flange to be continuously welded along the outside as well as the inside of the corrugations, as indicated at I4 and I5. The welding of the roof on the corrugated inner cover provides a pressure vessel when the bottom is sealed.

A plurality of bracing hoops are secured at spaced intervals to the exterior of the corrugated cylinder. The hoop or bands I6, I I and [8 are uniformly spaced at substantially equal distances from one another. It is preferable to locate a band at the zone of highest temperature, which may not be at the positions shown. The zone of highest temperature is determined by the construction of the furnace in which the inner cover is to be used. The hoops or bands are preferably welded to the crest of each corrugation and they amaeoa embrace the whole of the exterior of the corrugated cylinder and prevent any displacement of individual corrugationscircumferentially of the cover,- yet 'the troughs or inner portion of the corrugations are free to expand or contract and thus relieve the-outer portions of the corrugations of internal strains or stress.

The material making up these cylindrical inner covers may be mild steel or stainless steel.

' The mild steel covers may be used for normalizing up to temperatures approximating 1,650 F. whereas stainless steel covers will successfully operate at 2,100 F. The low carbon steel should be at least one-fourth to three-eighths inch plate; whereas the stainless steel may be made from one-eighth inch or less. The hoops or bands are preferably'stainless steel whether placed on mild or stainless steel corrugated cylinders.

A pair of hooks or eyes, such as shown at 20 and 2|, are welded to the base plates 22 that span one or more corrugations and are welded thereto for the purpose of hoisting the same. In order to prevent the hoisting chain from injuring the roof i2, a pair of bridge guard-straps 23 and 24 are secured to one or more corrugations adjacent their ends but arch outwardly beyond the edge of the roof flange IS. The hoisting cable or chain will engage these'bridge guard straps and will not injure the roof brim.

' The bottom edge or foot of the inner annealing cover is preferably reinforced by the bar 25 which is in the form of a ring that is just wide enough to hold a weld around the crests on both sides of the corrugations. This ring is welded to the corrugations on both sides thereof. Such a reinforcing ring is shown in Fig. 4 and is preferably made of three-eighths material. The ring 25in Fig. 1 has an annular'depending band 26 welded to the inner lower edge. The interior of the band 26 represents the smallest inside diameter of the cover and is substantially flush with the corrugations. This band may be ten' or more inches wide and is used not only to stiffen or reinforce the bottom of the annealing inner cover, but also functions as a sand sealing element. The sand is placed in a deep annulartrough and the band 26 is lowered thereinto when placed over the steel to be annealed. The rin'g.25 and the band 26 may be fabricated from .an angle iron with a shorter band welded to one leg aligned therewith. Such a welded structure'appears the same as that shown in Fig. 1.

In the structure of Fig. 5 the ring 25 is omitted and the band 21 is frusto conical. The bottom edge of the plates 2 are scalloped so that when the corrugationsare' formed they provide a continuous frusto conical surface to rec'eivethe frusto conical band- 21 with its upper edge extending to the smallest inside diameter of the corrugated cylindrical wall and is scalloped to follow the corrugations.

In the structure 'of Fig. 6 the ring bar 25 is secured to the bottom of the corrugated cylinder l and the depending-frusto conical band 21 is welded to the inner lower edge 28 and is further reinforced by the outer hoop 28 that extends from the outer edge 30 of the ring 25 to a point midway along the 'frusto conical band 21. The outer reinforcing hoop 29 may have openings as illustrated at 3! to permit-the circulation of air. The lower outer edge 32 of the frustoconical band 21 may have additional attachments for cooperating with different types of seals such as an oil seal. These bands may be normal to the rings 25 or angular thereto and they may be secured to the ring at any position therealong but it is preferable to have them joined at the inner lower edge of the ring.

In Fig. 7 the annular band 21 is Welded to the intermediate portion of the ring 25 and is thus spaced from the inner lower edge 28 of the ring 25. This is not preferable as one cannot see the corner 28 to properly center it over the steel or the hearth.

In Fig. 8 the reinforcing bar or ring 33 is cut out to fit the corrugations. This ring may be used to replace the flat hoops I6, I I and I8 or the bottom bar ring 25 and may be placed on the inside or outside when used to replace the latter. This form of fitting reinforcing ring 33 aids in retaining the shape of the corrugations.

I claim:

1. A circular annealing inner cover consisting of a plurality of corrugated steel plates each arcuately curved transversely of the corrugations to a uniform radius of curvature selected and integrally connected to form a complete symmetrical cylinder of predetermined diameter, the crests and troughs of the corrugations being substantially circular and merge tangentially into one another, the adjacent plate edges matching to form a continuous series of uniform corrugations circumferentially of the inner cover, the spacing between crests and the depth of said corrugations selected to provide a surface area twice the wall area of a smooth cylinder having a diameter substantially equal to the smaller inside diameter of the corrugated cylinder, an upwardly dished roof having an integral annular flange, the width of which flange is equal to the depth of the corrugations which are continuously secured to said flange to provide a gas tight top, a plurality of spaced continuous hoops encircling and supported on the cylindrical wall to brace the same. and an annular reinforcing ring the width of which is equal to the depth of the corrugations continuously secured to the lower ends of the corrugations.

2. A circular annealing inner cover consisting of a plurality of corrugated steel plates each arcuately curved transversely of the corrugations to a uniform radius of curvature selected and integrally connected to form a complete symmetrical cylinder of predetermined diameter, the crests and troughs of the corrugations being substantially circular and merging tangentially into one another, the adjacent plate edges matching to form a continuous series of uniform corrugations circumferentially of the inner cover, the spacing between crests and the depth of said corrugations selected to provide a surface area twice the wall area of a smooth cylinder having a diameter substantially equal to the smaller inside diameter of the corrugated cylinder, an upwardly dished roof having an integral annular flange. the width of which flange is equal to the depth of the corrugations which are continuously secured to said flange to provide a gas tight" top, a plurality of spaced continuous hoops encircling and supported on the cylindrical wall to brace the same, an

' annular reinforcing ring, the width of which is equal to the depth of the corrugations, continuously secured to the lower ends of the corrugations, and an annular band having its upper edge continuously secured to said reinforcing ring and extending therebelow.

3. The structure 01' claim 2 characterized in that said reinforcing ring has its inner edge scalloped to fit said corrugations.

4. A circular annealing inner cover consisting of a plurality of corrugated steel plates each arcuately curved transversely of the corrugations to a uniform radius of curvature selected and integrally connected to form a complete cylinder of predetermined diameter, the crests and troughs of the corrugations being substantially circular and merging tangentially into one another, the adjacent plate edges matching to form a continuous series of uniform corrugations circumferentially of the inner cover, the Spacing between crests and the depth of said corrugations selected to provide a surface area twice the wall area of a smooth cylinder havin a diameter substantially equal to the smaller inside diameter of the corrugated cylinder, an upwardly dished roof having an integral annular flange, the width of which flange is equal to the depth of the corrugations which are continuously secured to said flange to provide a gas tight top, a plurality of spaced continuous hoops encircling and supported on the cylindrical wall to brace the same, an annular reinforcing ring, the width of which is equal to the depth of the corrugations, continuously secured to the lower ends of the corrugations, and an annular band having its upper edge continuously secured to the inner lower edge of said reinforcing ring and extending therebelow.

5. A circular annealin inner cover consisting of a plurality of corrugated steel plates each arcuately curved transversely of the corrugations to a uniform radius of curvature selected and integrally connected to form .a complete cylinder of predetermined diameter, the crests and troughs of the corrugations being substantially circular and merging tangentially into one another. the adjacent plate edges matching to form a continuous series of uniform corrugations circumferentially of the inner cover. the spacing between crests and the depth of said corrugations selected to provide a surface area twice the wall area of a smooth cylinder having a diameter substantially equal to the smaller inside diameter of the corrugated cylinder, an upwardly dished roof having an integral annular flange, the width of which flange is equal to the depth of the corrugations which are continuously secured to said flange to provide a gas tight top, a plurality of spaced continuous hoops encircling and supported on the cylindrical wall to brace the same, and an annular reinforcing frusto conical band continuously secured to the lower ends of said corrugations.

MORRIS L. JACOB.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 613,001 Wilson Oct. 25, 1898 994,995 Gray June 13, 1911 1,014,491 Lammine Jan. 9, 1912 1,684,391 Green Sept. 18, 1928 2,069,768 'Millan s Feb. 9. 1937 2,074,093 Millan Mar. 16, 1937 2,075,115 Hunter et al. Mar. 30, 1937 2,177,811 Richards Oct. 31, 1939 2,214,249 Koch et a1. ...*Sept. 10, 1940 

